1. Field of the Invention
The present invention relates generally to the field of electrical junction boxes. In particular, the invention relates to electrical junction boxes including integrally formed cable clamping means.
2. Description of the Prior Art
Electrical junction boxes are safety enclosures that are used to physically isolate parts of a circuit, and are typically used where branching or switching occurs. Openings are provided in the walls of a junction box to receive electrical cable, and the branching or switching circuitry is housed entirely within the box. Although junction boxes have traditionally been made out of metal, recently thermoplastics have been used.
It is considered highly desirable to provide means for clamping the electrical cable passing through the openings in the walls of the junction box. Without such clamping means, electrical cable could accidentally be pulled out of the junction box with resulting damage to the circuitry within the box. For ease of manufacture and use, it is further considered desirable for the cable clamping means to be integrally formed as part of the junction box.
Thus, for example, U.S. Pat. No. 4,605,816 discloses a molded plastic junction box with integrally formed clamping "arms" that are disposed across the cable openings. These clamping arms are deflectable to allow electrical cable to be passed through the openings, but are resilient enough so that a clamping arm "squeezes" the cable against a corresponding side of the cable opening. Each clamping arm and each corresponding cable opening side are provided with integrally formed teeth that cooperate with each other to engage and clamp the inserted cable.
U.S. Pat. No. 4,591,658 discloses a clamping attachment for use with an electrical junction box. The attachment is formed of a thermoplastic material and includes a resiliently flexible clamping leg that functions in a manner similar to the clamping arm disclosed in U.S. Pat. No. 4,605,816. The clamping attachment is provided at one end with an integrally formed mount for affixing the attachment proximate to cable openings in the junction box. The other end of the clamping attachment includes an integrally formed clamping head that at least partially overlies a given cable opening and is formed with serrations that bite into the surface of the cable. In one embodiment of the invention, as shown particularly in FIGS. 6, 9, 12, 15 and 18, the clamp leg forms a curved structure. The clamps have an apparently uniform cross section. When an electrical cable is passed through a cable opening, both the portion of the curve proximate to the mount and the central bend of the curve are urged open.
U.S. Pat. No. 4,724,282 discloses a clamping arrangement that is similar to the approach taken in U.S. Pat. No. 4,605,816, and U.S. Pat. No. 4,591,658. In U.S. Pat. No. 4,724,282, metal clips are disposed proximate to the cable openings. Similar to the above patents, insertion of an electrical cable through an opening in the box resiliently deflects the clip, and the cable is held in place by squeezing action by the clip against the wall of the junction box. U.S. Pat. No. 4,724,282 further discloses slots in which the clips are mounted.
U.S. Pat. Nos. 1,396,790, 4,402,565, 4,150,250 and 4,306,109 disclose various other arrangements for engaging and connecting electrical cable.